Silanes are applied to metal surfaces for several purposes including corrosion resistance and adhesion promotion. As an example, steel tire cord must adhere to the rubber in order to function properly. Steel does not bond well to rubber. To improve adhesion, the steel tire cord has been coated with a layer of brass. During the vulcanization process, the rubber forms a chemical bond with the brass. This rubber/metal bond is formed only with sulfur vulcanized rubber which requires a relatively high sulfur level, greater than 4 phr, as well as certain accelerators, i.e., a delayed action sulfonamide and cobalt in the form of cobalt naphthenate to achieve proper cure and good adhesion, as well as zinc oxide. The cobalt improves the stability of the rubber-brass bond. However, it also has a negative effect on the stability of the rubber network in that it accelerates reversion in the presence of oxygen at elevated temperatures. The increased sulfur and cobalt are believed to be necessary in order to achieve a satisfactory bond between the tire cord and the rubber.
It has been proposed to treat tire cord with various silane compositions in order to improve adhesion. This is disclosed, for example, in van Ooij U.S. Pat. No. 6,416,869; U.S. Pat. No. 6,756,079; and U.S. Pat. No. 6,919,469. The processes disclosed in these patents have various issues. One issue is the efficient application of the silane onto the tire cord. Some of these applications require that the silane be baked onto the tire cord for adequate adhesion.
Pending application Ser. No. 11/366,235, entitled “Method of Applying Silane Coating in Metal Compositions”, filed Mar. 2, 2006, and published Mar. 15, 2007, discloses an improved method of applying silanes to tire cords. The disclosure of this is hereby incorporated by reference. The present invention is intended to improve on the methods disclosed in this application.